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Number Theory from Iran TST 2017

Source: 2017 Iran TST third exam day1 p1

April 26, 2017
number theoryIranIranian TST

Problem Statement

Let n>1n>1 be an integer. Prove that there exists an integer n1mn2n-1 \ge m \ge \left \lfloor \frac{n}{2} \right \rfloor such that the following equation has integer solutions with am>0:a_m>0: amm+1+am+1m+2++an1n=1lcm(1,2,,n)\frac{a_{m}}{m+1}+\frac{a_{m+1}}{m+2}+ \cdots + \frac{a_{n-1}}{n}=\frac{1}{\textrm{lcm}\left ( 1,2, \cdots , n \right )}
Proposed by Navid Safaei